Although I'm no expert on the subject of human evolution, I have
developed a number of tools over the years for testing
hypotheses. One of these is illustrated by the phrase "What is
sauce for the goose is sauce for the gander". In this context,
it would seem that your hypothesis would work equally well for
Stumptail Macaques (Macaca arctoides), and come to that every
other primate.

Now that you have completed the physiological explanations, all
you have to do is to explain why the changes in testosterone
level only applied to human ancestors, and not to the ancestors
of any other primate, or mammal.